Please help me diagnose this.

My 'Bolt (2000 miles on the clock) makes a distinctive and worrisome sound under certain conditions. If I'm rolling slow (40 mph or so) in overdrive (or third, but it's more noticeable in OD) the engine makes a particular sound under very light throttle at low RPM. It sounds like a soft, pulsating, rythmic "ticking" or "flutter" from the exhaust. Not a "booming" sort of exhaust throb, but a higher-pitched, light, "airy" sound. There's nothing to be felt, just heard. It definitely follows engine rpm. I'm thinking that maybe I have a miss caused by a bad plug or coil pack.

As the throttle is applied and RPM increase, the phenomenon disappears. At WOT, the thing just roars and there is no indication of a "miss" or anything else afoul. The sound can only be heard at low RPM/speed and at very slight throttle openings. I've run a 13.9 bone-stock with this happening (not at WOT on the strip, of course).

I'm a bit confused, as I figure a bad coil or plug (a true "miss") would be very evident at WOT at 90 MPH. My 'Bolt seems to run just fine under these conditions.

Any ideas?

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Silver Y2K Lightning
Bone Stock w/ Duraliner, Ford Hitch Cover

Silver (matching) Y2K ML320 Benz
Burl (ML430) Shift ****

Beater 1992 Grand Prix
Commuter Mule

 

I had the same sound until I replaced my plugs. After some time of also hearing it, I actually started to feel the miss.The bad thing was that this was occuring the same time my BASSANI cats decided they had enough torture

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Spiro-"The Greek"
BLK. #1476

Best run to date
12.610 @107.49
Best 60` 1.81
@ 4800 lbs.
On Pump Fuel
_________________________
JDM Engineering- Ford Specialist
_________________________

Johnny Lightning Performance
http://www.webtechnik.com/johnnylightning

"Empty Pockets Racing"Drag Race Team NJ-DE
Spiro99SVT@aol.com

 

I've got a miss that is similar, but it is most prevelant at approx. 40-45mph in third gear. Mine is definately a miss....pops, sputters, etc. I've taken it to two different dealers and neither have solved the problem. So far I have a new pcm, new wires, all coils and plugs checked, and; on the side, the clunk still not fixed.
I'm taking my '99 L to the third dealership Wednesday where the shop foreman is an L racer up at Moroso. Hope to get the problem resolved.....will post when I have info.

Tim

 

Tim:

Get as much info as you can. Mine does the same thing. It is so subtle that sometimes I think it is my imagination - but I don't think so. I mentioned it when my intercooler was changed (plugs also changed), and apparently diagnostics shows nothing abnormal, but it seems to still do it. Like everyone else, it screams nice and smoothly at WOT.

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Sandy (Spider) Scott
Skydive69@msn.com
Apopka, Florida
99 White Lightning #2091 DOB 6-8-99
Airaid air box (S&B Filter) & Superchip
Kills:
Last 4 generation Mustang GT's (Including Cobra)
Audi S4
Dodge R/T